Rectifiers which convert AC to DC produce heat due to the resistance of the rectifier. This heat must be dissipated as fast as it is generated or the rectifiers will overheat and fail. U.S. Pat. No. 3,011,105 provides a heat exchange frame having a central cylindrical portion with a plurality of cooling arms extending outwardly from the outer surface thereof in longitudinal planes. A rectifier is disposed on each arm to transfer heat to the arm.